As disclosed in e.g. Patent Document 1, this kind of chip resistor conventionally includes a pair of terminal electrodes provided on ends of the insulating substrate which is in the form of a chip. The resistor film is formed on the upper surface of the insulating substrate to extend between the ends of the insulating substrate.
Patent Document 1: JP-A-H08-213202
Each of the terminal electrodes comprises an upper electrode formed on the upper surface of the insulating substrate to be electrically connected to the resistor film, a lower electrode formed on the lower surface of the insulating substrate and a side electrode formed on an end surface of the insulating substrate to overlap part of the upper electrode and part of the lower electrode. A solder plating layer is formed on the surfaces of the upper electrode, the lower electrode and the side electrode. The chip resistor is mounted on e.g. a printed board by soldering the paired terminal electrodes on to the board.
The resistor film of the chip resistor is formed with a trimming groove or a slit at a longitudinal edge thereof. By forming the trimming groove, the resistance of the chip resistor is set to lie within a predetermined allowable range. The width of the portion of the resistor film at which the trimming groove is formed is smaller than that of other portions.
When the chip resistor is energized, the resistor film is heated. Specifically, during the energization, the portion of the resistor film which has a relatively small width due to the provision of the trimming groove is mainly heated. The heat generated at this portion is transferred to the terminal electrodes at the ends of the insulating substrate, and more specifically, to the upper electrodes, and then transferred to the printed board through the side electrodes and the lower electrodes.
In this way, in this chip resistor, the heat generated at the resistor film is transferred to the printed board only in the longitudinal direction of the insulating substrate. Thus, the heat mainly generated at the portion of the resistor film which has a relatively small width due to the provision of the groove is not efficiently transferred to the printed board, so that the temperature of the resistor film may become too high.